Distributed System
Essay by Chanunkha • July 29, 2017 • Course Note • 1,468 Words (6 Pages) • 1,115 Views
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MZUZU UNIVERSITY
FACULTY OF INFORMATION SCIENCE AND COMMUNICATIONS
DEPARTMENT OF INFORMATION AND COMMUNICATION TECHNOLOGY
COURSE TITLE: DISTRIBUTED SYSTEMS
COURSE CODE: ICT3604
FROM: CHIMWEMWE SHABA
(PGDICTU/2B/11/15)
TO: MR REUBEN MOYO
TASK: MAKING SUMMARY
DATE: 07/07/2017
SUMMARY
Chapter 1: Introduction
Definition
Distributed system refers to a collection of independent computers that looks like a single coherent system.
Characteristics of Distributed System
- The differences between various computers and the ways in which they communicate are mostly hidden to the users.
- Users and applications can interact with a Distributed System in a consistent and uniform way, regardless of where and when interaction takes place
- Distributed System should be able to expand or scale
- Distributed systems are organized by the means of layer of software that is logically placed between high-level layer comprising users and applications and the layer below consisting of operating systems and basic communication facilities called middleware.
- All this aim at supporting heterogenous computers and networks while offering single-system view.
GOALS
The main goals of distributed system are
- Should make resource easily accessible
- Should be transparent- meaning should be able to hide resources
- Should be open
- Should be scalable- should give room for addition
- Making Resources Accessible
Main goal of distributed system is to make it easy for the users access remote resources and share them in a controlled and efficiency way.
Reasons for sharing:
- For economic reason
- For easy collaboration and exchange information
- Transparency
Distributed system is said to be transparent if it present itself to users and applications as it was single computer system
Types of Transparency
- Access transparency
- Location transparency
- Migration transparency
- Relocation transparency
- Replication transparency
- Concurrency transparency
- Failure transparency
- Openness
An open distributed system is the systems that provide services according to standard rules that describe the syntax and semantics of those services.
Goals for open distributed system are:
- Proper specifications are complete and neutral
- Easy to configure the system out of different components
- Scalability
System can be scalable with:
- Respect to its size
- Geographically
- Administratively
Scalability Problems
- Centralized services
- Centralized data
- Centralized algorithm
Note: When developing distributed system do not the following assumptions:
- Network is reliable
- Network is secure
- Network is homogenous
- Topology does not change
- Latency is zero
- Bandwidth is infinite
- Transport cost is zero
- There is one administrator
Types of Distributed system
- Distributed Computing system
Subdivided into:
- Cluster computing system
- Grid computing system
- Distributed information processing system
Primitives of Distributed processing system
- Begin-transaction
- End-transaction
- Abort transaction
- Read transaction
- Write
Characteristics of Transaction Processing system
- Atomic
- Consistent
- Isolated
- Durable
- Distributed Pervasiveness system
Requirements
- Embrace contextual change
- Encourage adhoc composition
- Recognize sharing as adefault
CHAPTER TWO-
Architecture
Organization of distributed system is mostly about the software components that constitute the system.
These softwares help us to know how different software components are to be organized and how they should interact.
Architectural Styles
There are several architectural styles (logical styles). Important ones are:
- Layered architectures
-components organized in layered fashion
-requests go down the hierarchy while results flow upward
- Object base architecture
-far loose organization follow this style
- Data centred architecture
-evolve around the idea that process communicate through a common (passive or active) repository
- Event based architecture
-processes communicate through the propagation of events
-sometimes carry data
System Architectures
Important styles of hardware architecture for distributed system are
- Centralized Architecture
-in this one there are
1. basic client-server
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